The present invention relates to a method for patterning a metal layer by dry etching for use, in particular, in a process for fabricating a semiconductor device.
FIGS. 22-29 are cross-sectional views illustrating a conventional process to make a pattern of a metal layer.
The process comprising:
(1) Forming a 1.0 .mu.m-thick SiO.sub.2 (silicon dioxide) layer 21 and a 1.0 .mu.-thick AlSi (Alluminum alloy including silicon) layer 22 on a Si (silicon) substrate 20. [FIG. 22]
(2) Depositing a 3-layer resist consisting of a first resist layer as the lower layer 23, SOG (Spin-on-glass) as the middle layer 24, and a second resist layer as the upper layer 25 on the AlSi layer 22. [FIG. 23]
(3) Patterning the upper layer 25 using conventional photographic technology, and etching the middle layer 24. [FIG. 23]
(4) Removing the upper layer 25 and etching the lower layer 23 using the middle layer 24 as an etching mask. An inevitable problem in this process is the deposition of products 40 which result from a reaction between the etchant and the surface of the AlSi layer 22. [FIG. 25]
(5) Removing the middle layer 24. [FIG. 25]
(6) Etching the AlSi layer 22 using the lower layer 23 as a mask.
Inevitably, a portion of the etching products 41 is deposited on the wide wall layer 23. [FIG. 27]
(7) Removing the lower layer 23, leaving so-called "rabbit ears" at the shoulders of the patterned AlSi 22. [FIG. 28]
(8) Depositing a final passivation layer 27. [FIG. 29]
In a conventional dry etching metal patterning process as described above, "rabbit ears" on the shoulder of the patterned metal layer causes deterioration of the coverage of the passivation layer thereon. Specifically, the passivation layer tends to develop cracks and/or pinholes. Accordingly, semiconductor devices fabricated in this conventional process may suffer from poor reliability.